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← The last living members of an extinct species - Jan Stejskal

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Zeige Revision 1 erzeugt am 08/12/2020 von lauren mcalpine .

  1. In the savannahs of Kenya, two female
    northern white rhinos, Nájin and Fatu,
  2. munch contentedly on the grass.
  3. At the time of this video’s publication,
  4. these are the last two known
    northern white rhinos left on Earth.
  5. Their species is functionally extinct—
  6. without a male,
    Nájin and Fatu can’t reproduce.
  7. And yet, there’s still hope to revive
    the northern white rhino.

  8. How can that be?
  9. The story starts about 50 years ago,

  10. when poachers began illegally hunting
    thousands of rhinos
  11. across Africa for their horns.
  12. This, combined with civil wars
    in their territory,
  13. decimated northern white rhino
    populations.
  14. Concerned conservationists began trying
    to breed them in captivity in the 1970s,
  15. collecting and storing semen from males.
  16. Only four rhinos were ultimately born
    through the ambitious breeding program.
  17. Nájin, and her daughter Fatu
    were the last two.
  18. In 2014, conservationists discovered
    that neither can have a calf.

  19. Though Nájin gave birth to Fatu,
    she now has weak hindlegs,
  20. which could harm her health
    if she became pregnant again.
  21. Fatu, meanwhile,
    has a degenerated uterine lining.
  22. Then, the last northern white rhino male
    of the species, Sudan, died in 2018.
  23. But there was one glimmer of hope:
    artificial reproduction.
  24. With no living males and no females
    able to carry a pregnancy,
  25. this is a complicated and risky process
    to say the least.
  26. Though scientists had stored semen,
    they would have to collect the eggs—
  27. a complex procedure that requires a female
    to be sedated for up to two hours.
  28. Then, they’d create a viable embryo
    in the lab—
  29. something that had never been done before,
    and no one knew how to do.
  30. Even that was just the beginning—
  31. a surrogate mother
    of another rhino species
  32. would have to carry the embryo to term.
  33. Females of a closely related species,
    the southern white rhino,

  34. became both the key to developing
    a rhino embryo in a lab
  35. and the leading candidates
    for surrogate mothers.
  36. Northern and southern white rhinos
    diverged about a million of years ago
  37. into separate— though still
    closely-related— species.
  38. They inhabit different regions, and have
    slightly different physical traits.
  39. In a fortunate coincidence,
    several female southern white rhinos

  40. needed treatment
    for their own reproductive problems,
  41. and researchers could collect eggs
    as part of that treatment.
  42. In Dvůr Králové Zoo in October 2015,
  43. experts of IZW Berlin began collecting
    eggs from southern white rhinos
  44. and sending them to Avantea, an animal
    reproduction laboratory in Italy.
  45. There, scientists developed and perfected
    a technique to create a viable embryo.
  46. Once they mastered the technique,

  47. researchers extracted Nájin and Fatu’s
    eggs on August 22, 2019
  48. and flew them to Italy.
  49. Three days later, they fertilized
    the eggs with sperm
  50. from a northern white rhino male.
  51. After another week, two of the eggs
    made it to the stage of development
  52. when the embryo can be frozen
    and preserved for future.
  53. Another collection in December 2019
    produced one more embryo.
  54. As of early 2020, the plan is to collect
    Nájin and Fatu’s eggs three times a year
  55. if they’re healthy enough.
  56. In the meantime,
    researchers are looking for

  57. promising southern white rhino
    surrogate mothers—
  58. ideally who’ve carried a pregnancy
    to term before.
  59. The surrogacy plan
    is somewhat of a leap of faith—
  60. southern and northern white rhinos
    have interbred
  61. both during the last glacial period
    and more recently in 1977,
  62. so researchers are optimistic
    a southern white rhino
  63. would be able to carry
    a northern white rhino to term.
  64. Also, the two species’ pregnancies
    are the same length.
  65. Still, transferring an embryo
    to a rhino is tricky
  66. because of the shape of the cervix.
  67. The ultimate goal,
    which will take decades,

  68. is to establish a breeding population
    of northern white rhinos
  69. in their original range.
  70. Studies suggest that we have samples
    from enough individuals
  71. to recreate a population with the genetic
    diversity the species had a century ago.
  72. Though the specifics
    of this effort are unique,

  73. as more species face critical endangerment
    or functional extinction,
  74. it’s also an arena for big questions:
  75. do we have a responsibility to try
    to bring species back from the brink,
  76. especially when human actions
    brought them there in the first place?
  77. Are there limits to the effort
    we should expend
  78. on saving animals threatened
    with extinction?